Overview

A class action lawsuit has been filed against MoonLake Immunotherapeutics (“MoonLake” or the “Company”) and certain of the Company’s current senior executive officers alleging violations of the federal securities laws. The Company’s common stock trades on the NASDAQ stock exchange under the ticker symbol “MLTX”

The MoonLake class action lawsuit was brought on behalf of all persons and entities who purchased or otherwise acquired MoonLake common stock between March 10, 2024, through September 29, 2025, both dates inclusive, (the “Class Period”).

The lawsuit alleges that MoonLake and its executive officers misled investors about the efficacy and competitive potential of its only drug candidate, sonelokimab (SLK), a Nanobody-based therapy developed to treat inflammatory diseases such as hidradenitis suppurativa (HS), psoriatic arthritis, psoriasis, and axial spondyloarthritis. MoonLake, a Swiss clinical-stage biotechnology company, began its Phase 2b MIRA trial of SLK for moderate-to-severe HS in May 2022 and reported positive topline results in June 2023, meeting its primary endpoint. Follow-up data released in October 2023 showed further improvement with continued treatment, and by early 2024, both the FDA and EMA had endorsed MoonLake’s proposed Phase 3 program. The company launched its Phase 3 VELA-1 and VELA-2 trials in May 2024.

SLK is based on a proprietary Nanobody structure—an engineered, smaller version of an antibody fragment—which differs from traditional monoclonal antibodies in both size and structure. MoonLake positioned SLK as a potentially superior therapy to Union Chimique Belge’s (UCB) BIMZELX (bimekizumab-bkzx), an FDA-approved monoclonal antibody treatment for HS that targets the same inflammatory cytokines, IL-17A and IL-17F. Throughout the class period, MoonLake executives emphasized SLK’s unique Nanobody structure, claiming it provided increased tissue penetration and would deliver enhanced clinical efficacy compared to traditional monoclonal antibodies.

The lawsuit alleges that these representations were materially false and misleading. Specifically, defendants allegedly failed to disclose that SLK and BIMZELX share identical molecular targets, that SLK’s Nanobody structure would not provide a superior therapeutic benefit, and that the supposed advantage of increased tissue penetration would not result in improved clinical outcomes. As a result, MoonLake allegedly lacked a reasonable basis for its positive statements about SLK’s efficacy and competitive edge over monoclonal antibody-based drugs.

On September 28, 2025, MoonLake announced 16-week results from its Phase 3 VELA program, revealing that SLK failed to demonstrate competitive efficacy relative to BIMZELX. The news triggered a severe market reaction, with MoonLake’s stock price plunging $55.75 per share, or 89.9%, to close at $6.24 on September 29, 2025.

The lawsuit alleges that, because of defendants’ false and misleading statements and omissions, investors were misled about SLK’s true potential and the company’s prospects for success, resulting in substantial financial losses when the disappointing trial results were disclosed.

*          *          *

If you purchased or otherwise acquired MoonLake common stock between March 10, 2024, through September 29, 2025, both dates inclusive, and you wish to serve as lead plaintiff in this lawsuit, we encourage you to submit your information to DiCello Levitt LLP via the form on this page. 

You can also contact DiCello Levitt partner Brian O’Mara by calling (888) 287-9005 or at investors@dicellolevitt.com. 

The deadline to apply to the Court to serve as lead plaintiff in the MoonLake class action lawsuit is December 15, 2025.